Consider new entity/resource to allow more flexible grouping/summing of academic credits

This ticket relates to DATASTD-1390. The relevant comment from that ticket is:

I am posting a new idea to this case as well. Is the purpose of the SAR and Course Transcripts are being used to determine a student's Credit History and Graduation progress? If this is correct, can we consider a different model with new resource that is called Transcript Credits which collects all transcript credits for a student based on the Academic Subject Descriptor? The Academic Subject Descriptor is required on Courses and manually added Transcript records to be counted in Credit History and assume that most SIS's operate in a similar manner.

The SAR and Course Transcripts will still have value to view the detailed data but a Credit History resource and be used to track the actual Credit progress for a student. Graduation Plans are really tracked based on a Credit Group (ie. Math, Science) which can be aligned to a Academic Subject Descriptor.